1. Field of the Invention
This invention relates to novel dialkyl peroxides and a method of producing the same as well as a use thereof.
2. Related Art Statement
The photopolymerization or photocuring method for photopolymerizable (photocurable) monomer and photopolymerizable (photocurable) resin composition can rapidly be carried out at a low temperature as compared with thermal polymerization, thermal curing and oxidation curing methods, so that it has many merits such as improvement of productivity, energy-saving, non-pollution and the like. Furthermore, selective curing is made possible. Therefore, the photopolymerization or photocuring method is widely used in application for printing ink, paint, adhesive, resin letterpress, working of printed circuit board and the like.
In the photopolymerization or photocuring method, various initiators have been developed. For example, there are known photopolymerization initiators producing radicals under an influence of ultraviolet ray such as benzoin, benzoin ethers, benzyl, aryldiazonium salt, benzophenone derivatives, acetophenone derivatives, xanthates, thioxanthones, halogenated hydrocarbons and the like [Journal of Oil and Color Chemistry Association, vol. 59, pp 166-171 (1976)].
Furthermore, it is known that organic peroxides such as benzoyl peroxide, di-t-butyl peroxide and the like can be used as a photopolymerization initiator. However, these organic peroxides generally absorb only a light of not more than 320 nm [Chemical Review, vol. 68, pp 125-151 (1965)]. Although it has been attempted to use the organic peroxide together with a photosensitizer, it has been reported that the efficiency of light energy transmitted from the photosensitizer to the organic peroxide is low and the photolysis efficiency of the organic peroxide lowers, and particularly di-t-butyl peroxide as a dialkyl type organic peroxide produces no photosensitized decomposition in its molecule [Journal of the American Chemical Society, vol. 87, pp 3413-3417 (1965)].
In order to solve the above problem, ester-type organic peroxides containing benzophenone group as a light absorbing group in its molecule have been developed (U.S. Pat. No. 4,416,826, Japanese Patent laid open No. 59-197401). However, such a compound has drawbacks that the storing stability in dark room is poor and the cured resin is yellowed.
The above conventional photopolymerization initiators are useful, but have still some drawbacks to be solved. For instance, there are the following problems:
(1) benzoin and benzoin ethers are poor in the storing stability in dark room; PA0 (2) benzophenone derivatives are used together with an amine or the like, but the resulting polymer or cured product is yellowed; PA0 (3) thioxanthones are low in the solubility to monomer or resin; and PA0 (4) the ester-type peroxide containing the light absorbing group is poor in the thermal stability and the cured resin is yellowed.